I'm just switching from extract to AG and was trying to figure out how to to batch sparging larger gravity beers. I'm currently working on a Maibock that is, hopefully, going to be around 1.065. Which I understand isn't crazy huge, but my tun is 28 quarts, and my grain bill is about 15 lbs. which leaves me thinking I need about 15-17 (3.75-4.25 gallons) quarts of water to mash with. I know that I'm not going to get that entire amount of liquid back, but at the same time I don't think I can do 3 sparging batches. So I'm a bit confused should I do this just twice. I'm thinking that my OG will be to high, but then three times and I'm going to have a hell of alot of liquid to boil. What am I missing?

If you skip the mashout, you should be able to drain your first runnings, and then do a first batch sparge, drain, and then do a second batch sparge and drain (that would be your 'third' runnings, so I'll call it a three part batch sparge). Since I still don't have BTP up and running again, I can't look back at my old recipes, but I'm pretty sure that the amount of water that I used each time for the two sparges was definitely not as much as my original strike water and probably not even as much as the volume of my first runnings. But in my judgement, if really doesn't need to be. What you want to do is take the initial target volume -- your pre-boil kettle volume -- and subtract from that the volume of your first runnings, and then divide the remainder in half and add that much sparge water for each of your two sparges. Since your grain is already saturated, you should be able to drain the same amount of liquid that you add for your two sparges. Some people do just a single sparge, but my "theory" is that you won't reach the same efficiency. But since I can't recall ever actually trying it both ways and comparing, I can't say for certain. Hope that helps.

EDIT: I meant to add that I VERY seldom do a mash out because by adding that extra amount of water, you really have that much less water available to rinse the sugar our of your grains, which is the whole purpose of sparging. And it generally isn't necessary for me anyway because I drain the first runnings so quickly and then put that pot on the stove to start heating up while I do my sparging; after first runnings, both sparges including vorlaufs probably don't take more than 15 minutes, if that long, and I use 170F sparge water so I'm almost mashing out the last two runnings (sparges) as it is.